The fuel tanks on some tractors have an odd shaped geometry in order to take advantage of every usable cubic inch of space, thereby providing maximum volume for fuel storage. The odd shaped geometry may result in the trapping of air pockets in a tank as it is being filled, and the air pockets may cause fuel pressure splash-back particularly as the fuel level in the tank approaches the full condition. This results in the loss of expensive fuel and harm to the environment.
Other tractors have fuel tanks which, although rectangular in shape, are of large capacity and accordingly pumps having high fuel transfer rates are used to fill them. Refueling with these pumps should be closely monitored to prevent over-fill and the dispersion of costly fuel into the environment. However, experience has shown that there is a tendency on the part of tractor operators to start a fill operation and then leave it unattended while performing other service on the tractor, intending to return before the tank is full. This is particularly true of slow-fill operations (gravity feed) and sometimes true of fast-fill (pumped) operations where a typical tank with a capacity in excess of 200 gallons may take 3-5 minutes to fill. An operator frequently over-estimates the required fill time and this results in a considerable volume of fuel being spilled onto the ground, particularly if it is being pumped.